Method for driving a light-emitting unit and circuit therefor

Abstract

A driver circuit is provided which comprises a series-connected unit having a light-emitting element and a current limiting inductor directly connected to the light-emitting element, a regenerative diode which is connected in parallel to the series-connected unit and which regenerates energy stored in the current limiting inductor, a transistor which controls a current flowing through the light-emitting element and the current limiting inductor, and a controller which controls an operation of the transistor, wherein the controller controls the transistor according to a voltage value of a power supply applied to the light-emitting element.

What is claimed is: 
     
       1. A method for driving a light emitting unit, comprising:
 providing the light emitting unit and a switching element, the light emitting unit having an input and an output, wherein the input comprises an anode of a light emitting diode and the output comprises a terminal of a first inductor, and the switching element coupled to the output of the light emitting unit; 
 providing a switching element having a control terminal and first and second conducting terminals, the first conducting terminal coupled to the second terminal of the light emitting unit; 
 providing a control element having a supply input coupled for receiving an inductor signal; 
 providing a second inductor having first and second terminals, the first terminal of the second inductor coupled to the first input of the first controller, the second inductor configured to be electromagnetically coupled to the first inductor; 
 providing a third inductor having first and second terminals, the third inductor configured to be electromagnetically coupled to the first inductor, and configured to provide energy stored in the third inductor to an external circuit; 
 providing a first voltage at the input of light emitting unit; 
 continuously monitoring the first voltage to generate a monitor signal; 
 generating an output signal from the light emitting unit in response to a state of the switching element; and 
 using the monitor signal to control the switching element in response to the first voltage. 
 
     
     
       2. The method of  claim 1 , further including setting the state of the switching element in response to control signal generated by a control element. 
     
     
       3. The method of  claim 2 , wherein using the monitor signal to control the switching element in response to the first voltage includes using the monitor signal to control the control element. 
     
     
       4. The method of  claim 3 , further including generating a comparison signal in response to comparing the monitor signal with a reference voltage. 
     
     
       5. The method of  claim 4 , further including generating a control signal in response to the comparison signal and using the control signal to control the control element. 
     
     
       6. The method of  claim 5 , wherein using the control signal to control the control element comprises configuring the control signal to turn off the switching element. 
     
     
       7. The method of  claim 6 , wherein generating the monitoring signal includes voltage dividing the first voltage to a form a divided voltage. 
     
     
       8. The method of  claim 7 , further including enabling the control element to control the switching element in response to the divided voltage being greater than the reference voltage. 
     
     
       9. The method of  claim 8 , further including generating a first current in response to turning on the switching element, wherein the first current flows through the light emitting unit. 
     
     
       10. The method of  claim 6 , further including disabling the control element from controlling the switching element in response to the divided voltage being less than the reference voltage. 
     
     
       11. The method of  claim 2 , wherein setting the state of the switching element comprises turning on the switching element, wherein a first current flows through the light emitting unit. 
     
     
       12. A method for driving a light emitting unit, comprising:
 providing the light emitting unit having first and second terminals, wherein the first terminal comprises an anode of a light emitting diode and the second terminal comprises a terminal of an inductor; 
 providing a switching element having a control terminal and first and second conducting terminals, the first conducting terminal coupled to the second terminal of the light emitting unit; 
 providing a control element having a supply input coupled for receiving an inductor signal; 
 providing a first voltage at the input of light emitting unit; 
 using the first voltage to provide power to the control element in response to operating in a first operating mode; 
 configuring the switching element to be in an off state; 
 generating a regenerative signal in response to the switching element being in the off state; 
 generating a supply signal using a second inductor electromagnetically coupled to the first inductor; 
 using the supply signal to operate the control element; 
 electromagnetically coupling a third inductor to the first inductor; and 
 supplying electromagnetic energy stored in the third inductor to an external circuit in response to switching the switching element to an off state. 
 
     
     
       13. The method of  claim 12 , further including:
 detecting a ringing signal on the first voltage in response to turning off the switching element; and 
 using the detected ringing signal as a trigger signal to turn on the switching element. 
 
     
     
       14. The method of  claim 12 , wherein providing the light emitting unit comprises providing one or more light emitting elements coupled in series with a first inductor. 
     
     
       15. The method of  claim 14 , further including:
 detecting an inductor signal from the first inductor; and 
 using the inductor signal to change a state of the switching element. 
 
     
     
       16. The method of  claim 15 , wherein changing the state of the switching element comprises turning on the switching element. 
     
     
       17. The method of  claim 16 , further including:
 generating a current detection signal in response to turning on the switching element; 
 generating a comparison signal in response to comparing the current detection signal with a first reference voltage; and 
 turning off the switching element in response to the comparison signal. 
 
     
     
       18. A driver circuit, comprising:
 a series-connected unit having a light-emitting element having an input and an output and a first inductor having first and second terminals, the first terminal coupled to the output of the light-emitting element; 
 a switching element having a control terminal and first and second current conducting terminals; 
 a first controller having a first input and an output, the output coupled to the control terminal of the switching element; 
 a second inductor having first and second terminals, the first terminal of the second inductor coupled to the first input of the first controller, the second inductor configured to be electromagnetically coupled to the first inductor; 
 a third inductor having first and second terminals, the third inductor configured to be electromagnetically coupled to the first inductor, and configured to provide energy stored in the third inductor to an external circuit.